Various kinds of functional devices to be used in electronic devices such as MEMS elements are delicate components having a sensing section and a driving section, and are often packaged while being hermetically sealed for preventing deterioration of functions due to deposition of particles etc. These hermetic sealing packages are produced in the following manner: one substrate on which a semiconductor element is mounted, and the other substrate (sometimes also referred to as a cap, a cover and the like) are bonded to each other with a sealing material interposed between both the substrates, and are hermetically sealed.
Here, as a sealing material to be used in production of a package, a brazing material (e.g. Au—Sn-based brazing material etc.) has been widely used heretofore. However, with a brazing material, the bonding temperature (the melting temperature of a brazing material) is high, and a sealing material with which bonding can be performed at a lower temperature has been desired. Against such a background, the present inventors have developed a sealing method using a metal paste containing a predetermined metal powder as a method which enables low-temperature bonding and improves sealing property (Patent Document 1).
In the sealing method using a metal paste as developed by the present inventors, a metal paste is applied to at least one substrate, and sintered to obtain a metal powder sintered body, and the metal powder sintered body is used as a sealing material. A pair of substrates are pressurized to be bonded to each other with the metal powder sintered body as a sealing material being interposed between the substrates. Here, the sealing material is pressurized to be densified to the extent that the sealing material is almost as dense as a bulk body.